A U.S. Forest Service Officer on foot patrol along a popular trail in Utah made a shocking discovery last week. A couple of crazy men rigged the entrances to a rudimentary shelter with booby traps (http://fox13now.com/2012/04/21/two-men-arrested-for-setting-traps-on-hiking-trail/). People could have died. According to the Utah Country Sheriff's Office (http://www.utahcountyonline.org/Dept/Sheriff/Media/PressReleaseArchiveDetails.asp?ID=92179):
On April 16, 2012, U.S. Forest Service Law Enforcement Officer James Schoeffler was on foot patrol in this area when he came across one of these shelters. This particular shelter is known locally as "The Fort". Because of his time in the military Officer Schoeffler has extensive experience with identifying booby trap devices. As he investigated the shelter he noticed what appeared to be a trip wire near the ground at an entrance. Upon further investigation he discovered that the trip wire led to a booby trap device which was made with a large rock, sticks sharpened at both ends, and was held together with rope. This device was situated in such a way that when contact was made with the trip wire it would swing toward an unsuspecting hiker or camper. It was hung where it would most likely swing to and hit the head or face of the hiker or camper. In a second entrance to the shelter Officer Schoeffler found a second trip wire. This wire was configured so as to trip a person, possibly causing them to fall forward onto sharpened sticks placed in the ground.
http://gizmodo.com/5904341/homicidal-lunatics-busted-rigging-a-popular-trail-with-deadly-medieval-booby-traps/